Process for improving aluminum alloy



Patented Dec. 29, 1936 UNITED STATES PROCESS FOR, IMPROVING ALULHNUM ALLOY Alfred J. Lyon, Dayton, Ohio No Drawing. Original application April 7, 1930,

Serial No. 442,468. D

ivided and this application July 5, 1934, Serial No. 733,861-

9 Claims.

-(Granted under the act of March 3, 1883, as

amended April 20, 1928; 370 0. o. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

My invention relates to the improvement of aluminum alloys containing copper as the principal alloying constituent with other elements in lesser amounts such as nickel, iron, silicon, magnesium, chromium, lithium, .calcium or manganese or any combination of these elements.

One object is to provide alloys of this type for use in cast and wrought parts, having improved physical properties, especially tensile strength, elongation and hardness; another object is to improve the soundness and eliminate porosity in alloys of this type used in the form of castings that must resist pressure such as cylinder heads and other parts of internal combustion engines; a further object is to provide a method of producing these improvements in a simple and inexpensive manner.

Aluminum copper alloys are known to be divided into two groups. The first group comprises those alloys containing from three to six per cent copper and includes numerous compositions used commercially in both the wrought and cast condition with and without heat treatment. The other group comprises those alloys containing greater than sixper cent copper and are used commercially in the cast condition with or without heat treatment.

My invention is based on the discovery that all or a part of the alloying constituents of aluminum base alloys may be incorporated into the alloys by the means of their chloride compounds thereby greatly afiecting the hardness, strength, ductility and soundness of castings or parts made from these alloys in accordance with methods well known to the art. The efiect upon the physical properties varies with the chloride compound used and the copper content which may vary from three to fifteen per cent, and the properties that are obtained are different than the properties that are obtained when the metal of the chloride compound is incorporated into the alloy by the usual and known methods. I am aware that certain chlorine compounds have been used as fluxes in 'connection with the melting of aluminum alloys for the purpose of cleansing the metal from impurities. My invention of course is not primarily concerned with this phase of' aluminum alloy treatment, altho I recognize that in the treatment of aluminum alloys in accordance with my invention this cleansing is incidental to the modifying effect or grain refining that the compounds have upon the alloy. For example the compound NH4C1 is well known to have a cleansing eflect upon aluminum and other alloys but does not Chemical composition: Copper-4.3 per cent, silicon-0.7 per cent, iron-0.5 per cent Tensile strength, lbs. per sq. in.

Elongation, in 2 ins. percent Brinell hardness With 0.5 percent ammonium chloride.

32, 400 With no additions Likewise ZnClz and NaCl are used in small amounts for the same purpose without any modifying effect.

United States Patent Number 1,676,856 to Alfred George Cooper Gwyer and Henry Wilfred Lewis Phillips of London, England, discloses the fact that the tensile strength and ductility of the aluminum-copper alloys can be increased. and the grain structure refined, by the addition of the alkaline earth metals, barium, strontium or'calcium. I am aware that the alkaline earth metal hydroxides, alkaline earth metals, fluorides, sodamide and the oxide compounds of the alkaline earth metals when introduced into aluminum alloys containing more than six per cent copper, in the molten condition have a modifying efiect and increase the strength, hardness and ductility of castings made from these alloys. I am also aware that the alkaline earth metals, their fluoride, oxide and hydroxide compounds and certain other metals such as bismuth, antimony, boron and manganese are known to improve the strength and ductility of aluminum alloys containing substantial amounts of silicon as the principal alloying constituent when added to the molten alloy. I have found by a series of tests upon aluminum alloys containing three to six per cent copper as the principal alloying constituent and with small amounts of iron and silicon as impurities that metals and elements that modify and refine the grain structure of aluminum copper alloys containing more than six per cent copper or aluminum alloys containing from three to fifteen per cent silicon as the principal alloying constituent, do not have the same efiect upon alloys of the type which are included in my invention. As an illustration I have added metallic sodium, potassium, potassium fluoride, sodium fluoride or lithium fluoride to aluminum copper alloys containing four per cent copper without improving the strength, ductility or hardness, but when I added lithium chloride in the same manner and in the same amounts to the molten alloy I obtained substantial improvements in the strength and ductility of the alloy when cast under the same conditions as the untreated alloy. This is in accordance with the known facts concerning the modification of aluminum alloys for the purpose of refining the grain structure and improving the physical properties. What happens in the case of aluminum-silicon, aluminum-iron, or alu- 5 minum-copper alloys of one class is no guide to what happens in the case of other alloys.

I am aware that aluminum is a metal frequently used as a reducing agent in-processes involving thereduction of oxides of metals. The Thermite process invented by Goldsmith is an example in which metallic oxides are reduced by aluminum. I have incorporated manganese for example into aluminum copper alloys by this principle by 'using the compound manganese dioxide but it has no modifying effect when added in this manner. e

In the preferred practice of the present invention, a copper-aluminum alloy is prepared in the usual manner by melting aluminum ingot which contains small amounts of iron and silicon as impurities, together with the copper and all or a part of other alloying constituents in the form of commercially pure metals or in the form of rich alloys of the alloying constituents with aluminum.

When the alloy is molten and has reached a temperature of approximately 700 degrees centigrade, I introduce the chloride compound of one or more of the alloying constituents as described hereinafter.

Chloride compounds are hydroscopic and before introducing them to the molten aluminum, they must be dried by heating to a temperature of approximately 100 C. for' several hours and. then crushed to break down lumps and crusts that form during the drying treatment, or they may be melted and poured into sticks or other forms of convenient size for introducing into the molten metal. i The. chlorides are then incorporated with the 40 molten aluminum alloy by wrapping weighed quantities in aluminum foil or paper and holding it beneath the surface of the molten metal. For this purpose a section of wrought iron pipe open at both ends is welded to an iron: rod or handle,

in such a manner that the section of pipe, ap-

proximately 4 inches in length and 1 inches in diameter, may be loweredbeneath the surface of the molten metal in a horizontal position. The chloride compounds in this manner are held beneath the surface of the metal until the reaction is completed. Stirring or agitation of the metal by mechanical means is not necessary as the reduction of the chlorides is accompanied by considerable agitation of the metal with an evolution of chlorine gas.

The chloride compounds can also be incorporated into the aluminum or aluminum alloys by other methods, such as pouring the molten metal into a crucible prd-heated with the chloride com- P unds in the bottom, or by stirring the powdered and dried salts into the molten metal. However, these methods do not produce as satisfactory results and I prefer to use the method first described. L

5 I have found that certain of the metal chlorides added to the aluminum alloys in the molten condition in accordance with this method caused an improvement in physical properties, but when remelted without further addition of these chlorides,

the gained strength, hardness and ductility are partially lost and in some instances causethe properties to be inferior to the untreated alloy. As an illustration, the following results were obtaiz-ed on standard test specimens cast from an alloy containing 4.3 percent copper, 0.5 percent iron, and 0.7 percent'silicon, in green sand and heat treated by a method well known to the art.

' Elonga- B Chloride Per- Tensile tion in added cent strength PS1 2 ins. Remarks .5

percent I a 0. 25 37, 300 7. 5 79 As treated. None 36, 490 7. 5 77 t remelt. None 34, 720 6. 3 76 2nd remclt. 10 non 0. 25 38,600 8.0 so As treated.

Do None 36, 970 7. 7 76 1st remelt. Do None 34, 580 6. 3 74 2nd remelt.

,900 7. a 75 As treated: 37, 650 9. 2 77 1st remelt.

,950 6.5 72 2nd remelt. 15

40, 820 7. 2 As treated. 40, 760 5. 5 88 1st remelt. 42, 140 5. 0 2nd remelt. 080 8. 0 90 As treated. 42, 620 7. 5 v 86 1st remclt. as, 367 s. 0 78 As treated. 20 36, 560 7. 0 78 1st remelt. 36, 400 7. 0 78 2nd remelt. 40, 630 9. 0 80 As treated. 39, 400 9. 0 81 1st remelt.

52, 250 l. 0 123 As treated.

500 0. 7 121 1st remelt. 25 47, 790 0.8 v 118 2nd rcmelt.

41, 000 9. 0 80 As treated. D0 None 39, 8. 5 81 1st remelt. Do None 37, 700 7. 5 80 2nd remelt.

ithium. 0. 50 38, 400 8. 8 77 AS treated.

Do None 39, 550 1o. 3 78 1st remelt. 30 Do None 40, 300 11.0 80 2nd remelt.

None 36, 910 5. 6 82 As mixed. 0 37,525 7. 5 80 1st remelt.

the strength and hardness. This is illustrated by the results tabulated in the following table, obtained on standard specimens cast in sand and 45 heat treated from an aluminum alloy containing 4.3 per cent copper and small amounts of silicon and iron.

Elonga- 50 Chloride Per- Tensile tion in 2: 1:?! Remarks added cent strength PSI 2 ins. Hess percent Nickel 0. 25 38, 367 8.0 78 1st remelt.

D 0. 25 630 9.0 80 2nd remelt. 55 Do 0. 50 39, 400 9. 0 81 3rd remelt, Do 0. 50' 38, 980 10.0 4th remelt.

0. 25 37, 300 7. 5 79 1st remclt. 0. 25 38, 450 8.7 80 2nd remelt. 0. 50. ,050 7. 3 79 3rd remelt, Do 0. 50 41,830 11.0 82 4th rernelt. 6O

0. 25 35,900 7. 3 75 1st remelt. 0.25 37,350 9. 5 74 2nd remelt. 0. 50 35, 880 9. 0 74 3rd remelt, 0. 50 33, 0%) 7. 7 73 4th remelt.

0. 25 52, 250 1. 0 123 1st remelt. 0. 25 37, 875 0. 5 122 2nd remelt. 65 0. 50 500 0. 5 119 3rd remelt. 0. 50 27, 250 117 4th remelt.

0. 25 40, 850 9. 0 81 1st remelt. 0. 25 100 6. O 80 2nd remelt. 0. 50 36, 050 5.0 79 3rd remelt. 0. 50' 36, 700 6.0 81 4th remelt. 70

Total chloride adding in process of remelting equals 1.5 percent.

In carrying out my invention in the preferred manner, it may be seen in the foregoing that specific amounts of the chloride compound must 75 Tensile strength, Elongation Brinell lbs. per sq. in. in 2", percent hardness ganese, percent A B C A B O A B O The results shownin Columns A" and C are for the purpose of illustrating theimproved prop- 1 erties I obtain by using the chloride compound, since it is well known to the art that the method of casting and the type of specimen has a pro-v found effect on the physical properties. The results in Columns A, B and C were obtained ganese was incorporated into the alloy, from which the results in Column C were obtained by means of manganese dioxide added to the molten alloy before pouring. I have found that the best results for a manganous chloride modified alloy of this type are obtained when manganous chloride is used in the amounts from about .4 to .5 per cent.

As another example of improving the properties of eliminating the defects from certain alloys of the type that are the subject of my invention, such as eliminating porosity, I melt an aluminum alloy containing 4 percent copper, 1 /2 percent magnesium, and 2 percent nickel in the usual manner and when the molten metal has reached a temperature of 700 C., I introduce nickelous chloride or cupric chloride or a mixture of nickelous and cupric chlorides in amounts greater than .75 per cent. (Less than .7 per cent nickelous chloride does not produce the result desired.) Other chloride compounds may be used for this purpose, but where zinc is used, for example, the strength of the alloy at high temperature is adversely affected. I

By introducing the chloride compounds of lithium or manganese or a combination thereof into the molten alloy in the manner already described and preferably in amounts from about .25 per cent to 1 per cent, the grain structure and the size of the particles of the alloying constituents are reduced and refined and consequently go into solid solution more quickly thus shortening the period of the usual heat treatment.

The alloys produced according to my invention may be utilized for any kind of casting, and such castings may be worked as by rolling, extruding, forging, drawing, etc. The results quoted for physical properties are based upon sand cast specimens and do not represent the maximum physical properties obtainable in castings or the properties of the materials in the wrought condition. It is well known that the tensile properties of cast alloys are greatly improved by casting in metal molds or by chilling and that the strength and hardness of a chill casting is increased to a marked degree by rolling or forging.

From these and other experiments, I have discovered that each of the chloride compounds added to the molten aluminum alloy of this type affect the physical properties of the heat treated castings in a manner that cannot be obtained by the addition of the metal of the compound; by the reduction of other compounds containing the metal by the addition of metal in the primary state; or by treating the metals with chlorine gas obtained by the reduction of' such compounds as ammonium chloride.

Therefore, in carrying out my invention in the preferred manner, I select one of the chloride compounds or a mixture of two or more chloride compounds that produce the special combination of properties such as strength, hardness or strength and ductility and soundness that may be required in the part or casting made from the alloy,

This application is a division of application Serial No. 442,468, filed Apr. 7, 1930, which has issued as Patent No. 1,965,604, dated July 10, 1934.

I claim:

1. A process for producing aluminum-copper alloy, which consists in the steps of melting together a mixture consisting predominately of aluminum and containing 3% to %copper as the principal alloying constituent, and thereafter incorporating in the molten alloy a material containing tin chloride.

2. A process for producing aluminum-copper alloy, which consists in the steps of melting together a mixture consisting predominately of alumaterial containing tin chloride in the molten alloy at a temperature of about 700 centigrade.

3. A process for producing aluminum-copper.

alloy, which consists in the steps of melting aluminum containing iron about 5% and silicon about .7%, together with copper about 4.3%, and thereafter introducing into the molten alloy a chloride of tin in a relatively limited amount.

4. A process for producing aluminum-copper alloy, which consists in the steps of melting aluminum containing iron about .5% and silicon about .7 together with copper about 4.3%, and thereafter adding to said molten alloy about 25% tin chloride.

5. A process of producing an aluminum-copper alloy which consists in the steps of melting together a mixture consisting predominately ,of aluminum containing 3% to 15% copper as the principal alloy constituent and thereafter incorporating a material containing tin chloride into said molten alloy at a temperature of about 700 centigrade.

6. A process of producing an aluminum-copper alloy which consists in the steps of melting together a mixture consisting predominately of aluminum containing 3% to 15% copper as the principal alloy constituent and thereafter incorporat ing a chloride of tin in a relatively limited amount into said molten alloy at a temperature of about 700 centigrade.

7. A process of producing an aluminum-copper alloy which consists in the steps of melting together a mixture consisting predominately of alu-v ing a dehydrated material containing tin chloride into said molten alloy.

9. A process of producing an aluminum-copper 'alloy which consists in the steps of melting together a mixture consisting predominately 0t aluminum containing 3% to 15% copper as the principal alloy constituent and thereafter incorporating a dehydrated material containing tin chloride into said molten alloy at a temperature of about 700 centigrade.

ALFRED J. LYON. 

